How do you calculate a date value in a stored procedure? This:
CStr(DateAdd("m", -6, Date))
Is the line in the original code and I am wondering if rather than pass the value to the stored procedure if I can calculate that value in the stored procedure but not sure how to do it?
If you are talking SQL Server then it has a dateadd function:
To duplicate your ASP Code it would look something like: DATEADD("m",-6,GETDATE())
Here's the list of SQL Server Date Functions:
http://msdn.microsoft.com/en-us/library/ms186724.aspx
In you stored procedure you can use GETDATE() to get the current date, unless you want to pass in the date, but, I tend to prefer to use the database computer's clock, so that all dates are based on the same clock.
Your question is bit vague, I am not certain if you want to calculate the date in the stored procedure, or get a date that was returned from a stored procedure, so I assumed the former.
Related
I am building a rails app, where the user picks up a date from a date picker and a time from the time picker. Both the date and time have been formatted using moment js to show the date and time in the following way:
moment().format('LL'); //January 23,2017
moment().format('LTS'); //1:17:54 PM
I read this answer with guidelines about selection of a proper column type.
Is there documentation for the Rails column types?
Ideally, I should be using :date, :time or :timestamp for this. But since the dates are formatted, should I be using :string instead?
Which would be the correct and appropriate column type to use in this situation?
If you want to store a time reference in your database you should use one of the types the database offers you. I'll explain this using MySQL (which is the one I have used the most) but the explanation should be similar in other database servers.
If you use a timestamp column you will be using just 4 bytes of storage, which is always a good new since it makes smaller indexes, uses less memory in temporal tables during the internal database operations and so on. However, timestamp has a smaller range than datetime so you will only be able to store values from year 1970 up to year 2038 more or less
If you use datetime you will be able to store a wider range (from year 1001 to year 9999) with the same precision (second). The bad consequence is that a higher range needs more memory, making it a bit slower.
There are some other differences between these two column types that don't fit in this answer, but you should keep an eye on before deciding.
If you use varchar, which is the default column type for text attributes in Ruby on Rails, you will be forced to convert from text to datetime and vice-versa every time you need to use that field. In addition, ordering or filtering on that column will be very inefficient because the database will need to convert all strings into dates before filtering or sorting, making it impossible to use indexes on that column.
If you need sub-second precision, you can use bigint to meet your requirements, as MySQL does not provide a date specific type for this purpose
In general, I recommend using timestamp if your application requirements fit the timestamp limitation. Otherwise, use datetime, but I strongly discourage you to use varchar for this purpose.
EDIT: Formatting
The way you store dates in database is completely different from the way you display it to the user. You can create a DateTime object using DateTime.new(year, month, day, hour, minute, second) and assign that object to your model. By the time you save it into database, ActiveRecord will be in charge of converting the DateTime object into the appropiate database format.
In order to display a value that is already stored in database in a specific format (in a view, API response, etc.) you can hava a look at other posts like this one.
You can have a timestamp column in your database, and then parse the request to a ruby datetime object like this:
d = Time.parse(params[:date])
t = Time.new(params[:time])
dt = DateTime.new(d.year, d.month, d.day, t.hour, t.min, t.sec, t.zone)
#now simply use dt to your datetime column
On Postgres you can save a ruby DateTime object straight into a postgres timestamp field, e.g
User.first.update_attribute('updated_at', dt )
Another option is to concatenate your date and time strings into one and then u can do a one-liner:
User.last.update_attribute('created_at', Time.parse('January 23,2017 1:17:54 PM'))
I'm pretty sure this will work on MySQL datetime or timestamp as well.
Credit to david grayson Ruby: combine Date and Time objects into a DateTime
I want to add time only as HH:MM to MS Access in Delphi.
It is shown as '21:21:00' in the Access table but it shows up as '30.12.1899 21:21:00' in my dbgrid.
ADOTable1.Active:=FALSE;
ADOTAble1.Open;
ADOTable1.Insert;
ADOTable1time.Value:=Strtotime(MaskEdit1.Text);
ADOTable1.post;
ADOTable1.Active:=TRUE;
Note: I changed editmask option to short time of TMaskEdit1
Thank in advance.
The data is correctly stored, it's just not displayed as you would like.
The Date/Time in Access as the Delphi TDateTime is storing casually spoken
the date in the integer part and the time in the fractional part.
To get the Time shown as desired just set the DisplayFormat property of your field to hh:nn:ss.
In the pictures below you can see the always same field formatted, not formatted and as float.
You need to tweak the formatting for that column of your dbgrid to only show the time component. Access only has a Date/Time column type (it does not have separate Date and Time column types) so a Date/Time value entered without a date part is stored as 1899-12-30 hh:mm:ss. If you are only interested in the time part then you just need to format the dbgrid column appropriately. (Access automatically does that for you in its own controls, ref: here.)
You can do it programatically, after you open the dataset:
TDateTimeField (FieldByName ('Time')).DisplayFormat:='HH:mm';
Change this date format which is in sqlite db 12/10/11 to 12-10-11 (mm-dd-yy) I am unable to do so .I am a noob in sqlite and have to parse this value SELECT strftime('%d-%m-%Y',Date) from report but I am getting null as sqlite db excepts value in mm-dd-yy so How do I convert format 12/10/11 to 12-10-11 (mm-dd-yy) .Thanks in advance .Really appreciate the help.
The short answer:
If you have a text string stored as "12/10/11" that you want reported as "12-10-11", you should use the replace(X,Y,Z) function, to replace occurrences of Y in X with Z. Thus:
SELECT replace('12/24/11','/','-');
will return:
12-10-11
The long answer:
First, dates do not actually exist as a proper datatype in SQLite. They're stored as either TEXT, REAL, or INTEGER values. See date and time datatype in SQLite. So it depends upon how your date was stored in the database.
Second, you seem to be implying that you stored the date in a "mm/dd/yy" format. That's not a valid/useful TEXT format to be storing date/time values (as the date cannot be sorted, cannot used in "greater than" and "less than" operations, cannot be used in SQLite date functions, etc.). You really want to store datetime values in one of the formats listed in the "Time strings" section of the date and time functions document.
So, generally you should store your date/time values in one of those formats, use NSDateFormatter to convert that to a NSDate when you retrieve it from the database. And when you want to display the date value in your app, use whatever format you want for output.
But, if you don't care that the dates are stored as text strings and are not effectively usable as dates in SQLite, then just treat it as a plain old TEXT string and use TEXT functions, such as replace(X,Y,Z) to replace occurrences of "/" with "-", as outlined above.
I want to store the date of an event in my database, but I want to do so without storing informations about seconds or anything smaller than seconds. Using Rails, in my migration I have the option to create a date column or a datetime column, the first one of which is too less accurate, and the second one is too much (up to the second and less). Which type should I choose to store such a date? Currently I'm using datetime and setting the seconds to a fixed value (e.g. 0) manually each time some date is set in the model.
Something like this:
self.date ||= Time.now.change(:sec => 0)
Am I totally out of track? Should I just use an integer field for each component of the date instead? (year, month, day, etc...) Or is datetime the correct type but I'm not understanding the purpose of it? (I think it's meant for timestamps and such things where seconds matter)
datetime is the correct type. And be sure to store it without time zone at time zone UTC:
http://derickrethans.nl/storing-date-time-in-database.html
At your option, use an SQL trigger to round your date to the minute on insert/update. It'll simplify your ruby code.
I want to let users specify a date that may or may not include a day and month (but will have at least the year.) The problem is when it is stored as a datetime in the DB; the missing day/month will be saved as default values and I'll lose the original format and meaning of the date.
My idea was to store the real format in a column as a string in addition to the datetime column. Then I could use the string column whenever I have to display the date and the datetime for everything else. The downside is an extra column for every date column in the table I want to display, and printing localized dates won't be as easy since I can't rely on the datetime value... I'll probably have to parse the string.
I'm hoping I've overlooked something and there might be an easier way.
(Note I'm using Rails if it matters for a solution.)
As proposed by Jhenzie, create a bitmask to show which parts of the date have been specified. 1 = Year, 2 = Month, 4 = Day, 8 = Hour (if you decide to get more specific) and then store that into another field.
The only way that I could think of doing it without requiring extra columns in your table would be to use jhenzie's method of using a bitmask, and then store that bitmask into the seconds part of your datetime column.
in your model only pay attention to the parts you care about. So you can store the entire date in your db, but you coalesce it before displaying it to the user.
The additional column could simple be used for specifying what part of the date time has been specified
1 = day
2 = month
4 = year
so 3 is day and month, 6 is month and year, 7 is all three. its a simple int at that point
If you store a string, don't partially reinvent ISO 8601 standard which covers the case you describe and more:
http://en.wikipedia.org/wiki/ISO_8601
Is it really necessary to store it as a datetime at all ? If not stored it as a string 2008 or 2008-8 or 2008-8-1 - split the string on hyphens when you pull it out and you're able to establish how specific the original input was
I'd probably store the datetime and an additional "precision" column to determine how to output it. For output, the precision column can map to a column that contains the corresponding formatting string ("YYYY-mm", etc) or it can contain the formatting string itself.
I don't know a lot about DB design, but I think a clean way to do it would be with boolean columns indicating if the user has input month and day (one column for each). Then, to save the given date, you would:
Store the date that the user input in a datetime column;
Set the boolean month column if the user has picked a month;
Set the boolean day column if the user has picked a day.
This way you know which parts of the datetime you can trust (i.e. what was input by the user).
Edit: it also would be much easier to understand than having an int field with cryptic values!
The informix database has this facility. When you define a date field you also specify a mask of the desired time & date attributes. Only these fields count when doing comparisons.
With varying levels of specificity, your best bet is to store them as simple nullable ints. Year, Month, Day. You can encapsulate the display logic in your presentation model or a Value Object in your domain.
Built-in time types represent an instant in time. You can use the built in types and create a column for precision (Year, Month, Day, Hour, Etc.) or you can create your own date structure and use nulls (or another invalid value) for empty portions.
For ruby at least - you could use this gem - partial-date
https://github.com/58bits/partial-date